Introduction
Parasitology is the study of parasites, their hosts, and the relationships between them. Parasites are organisms that live on or within a host organism, deriving nutrients at the host’s expense. They are classified into three main groups: protozoa (single-celled organisms), helminths (worms), and ectoparasites (such as ticks and lice). Parasitic infections are a major public health concern worldwide, particularly in tropical and subtropical regions where sanitation and healthcare infrastructure may be inadequate.
Branches of medical parasitology
helminthology: Is the study of parasitic worms (helminths) which include species that infect humans animals and plants. is it a branch of parasitology that focuses on the biology, classification, and impact of these worms on health
protozoology: Is the study of protozoan. single celled eukaryotic microorganisms
Ectoparasitology: Is the study of parasites that live on the external surface of their host. These include arthropods like fleas, lice, ticks, mites and mosquitoes, which can cause various disease in humans and animals.
Association of parasitic and host organisms
When there is an association between two organisms, their relationship one of the following types:
Mutualism: – is when the two-organisms benefit from the association.
Commensalisms: – when the parasite benefits from the host while the host neither benefited nor harmed.
Parasitism: – the parasite benefits from the association the later host usually suffers from the association.
host
host is any living organism that a protozoan parasite lives in or on to survive, grow, and reproduce. Some protozoa live harmlessly in their hosts, but others cause serious diseases. The relationship between protozoan and host can be as dramatic as any survival story—one thrives while the other suffers.
Types of hosts are as following
definitive hots: refers to the biological organism, the host, in which a parasite sexually reproduce. The parasite will grow and grow and reach sexual maturity while in the parasite, reproduce and continue the parasite’s species
Intermediate host: Infection of a host other than the normal host species. A parasite may or may not continue full development in host
Reservoir host: A wild or domestic animal which harbors a parasite and acts as sources of infections to humans .e.g. cats are reservoir hosts for toxoplasma gondii
Carrier host: A host harboring and disseminating a parasite but exhibiting no clinical sign
Types of carrier hosts:
Asymptomatic carrier: and organism that harbors a pathogen but does not show symptoms
Incubatory carrier: someone who spreads a pathogen during the incubation period before symptoms appear
Convalescent carrier: an organism that continues to spread a pathogen even after recovering from the illness.
Chronic carrier: an organism that carries and transmits a pathogen for a long time.
Accidental (incidental) host: Accidental host also called (incidental host) is a living organism that unintentionally becomes infected by a parasite but is not the parasite’s usual or preferred host.
A parasite may or may not continue full development in this host. e.g. humans can be accidental hosts for toxocara (a parasite typically found in dogs and cats)
Vector: Any arthropod or other living carrier which transport a pathogenic microorganism from an infected to non-infected host.
Biological vectors: Those vectors that complete the life cycle of a parasite. E.g. anopheles (vector of plasmodium
Mechanical (paratenic or transport) vectors: They are passive carriers of parasites, not essential in the life cycle e.g. house fly and cockroach as a mechanical vector for Amoebae, giardia etc.
